The Fischer-Tropsch process can be used for the conversion of (hydro)carbonaceous feedstocks into liquid and/or solid hydrocarbons. The feedstock, e.g. natural gas, associated gas, coal-bed methane, biomass, heavy oil residues, coal, is converted in a first step into a mixture of hydrogen and carbon monoxide (this mixture is often referred to as synthesis gas or syngas). The synthesis gas is then fed into a reactor where it is converted over a suitable catalyst at elevated temperature and pressure into paraffinic compounds ranging from methane to high molecular weight molecules comprising up to 200 carbon atoms, or, under particular circumstances, even more. Examples of the Fischer-Tropsch process are described in e.g. WO-A-02/02489, WO-A-01/76736, WO-A-02/07882, EP-A-510771 and EP-A-450861.
WO-A-2006/070018 describes a process wherein preferably coal is converted into a synthesis gas by means of partial oxidation. Part of the synthesis gas is subjected to a catalytic water shift process step and combined with non-shifted synthesis gas. The resulting mixture is used to perform a Fischer-Tropsch synthesis to obtain a paraffinic product. In this publication reference is made to the well-known gasification processes for coal.
Examples of well-known coal gasification processes are described in U.S. Pat. No. 4,836,146 and in WO-A-2004/005438. U.S. Pat. No. 4,836,146 describes a gasification system for a solid particulate comprising a gasification reactor and a synthesis gas cooling vessel. In this publication a method and apparatus is described for controlling rapping of the heat exchange surfaces as present in the separate cooling vessel. Rapping is required to avoid deposits to accumulate on the surfaces of the heat exchangers.
A problem with the syngas cooler of WO-A-2004/005438 and U.S. Pat. No. 4,836,146 is that the heat exchanging surfaces introduce a large complexity to the design of said apparatuses. Furthermore extensive measures like rapping are required to avoid deposits to accumulate on the heat exchanger surfaces. Another problem is that the heat exchanging surfaces are even more vulnerable to fouling from feedstocks with for instance a high alkaline content. There is thus a desire to process high alkaline feedstocks as well as a desire to provide more simple processes. This especially wherein the synthesis gas is used in a Fischer-Tropsch process, which in itself is already a complicated process.
EP-A-0400740 describes a process wherein syngas is produced by gasification of solid fuel in a reactor vessel equipped with tangential burners. The obtained slag flows downwardly while the syngas flows upwardly and is quenched in a single quench section located above the reactor.
The afore discussed gasification reactors have in common that the synthesis gas as produced flows substantially upwards and the slag flows substantially downwards relative to the gasification burners as present in said reactors. Thus, all these reactors have an outlet for slag, which is separate from the outlet for synthesis gas. These reactors have the advantage that large capacities per reactor are achievable. These reactors are different from a class of gasification reactors as for example described in EP-A-926441 and U.S. Pat. No. 4,946,476 where both slag and synthesis gas flow downwardly and wherein both the outlet for slag and synthesis gas are located at the lower end of the reactor.
It would be advantageous to provide a more simple process to prepare a paraffinic product from a solid carbonaceous feed using the ‘high capacity gasification reactors’ as described above.